Chlorpromazine (CPZ) is one of several phenothiazines known to have antimicrobial properties. It can inhibit mycobacteria, and was reported in the early literature to improve tuberculosis clinically. CPZ was tested here for its ability to inhibit the replication of Mycobacterium tuberculosis and Mycobacterium avium in cultured normal human macrophages, as determined by counts of viable bacteria at 0,4, and 7 days after bacterial infection of the macrophages. CPZ inhibited the intracellular bacteria at a concentration range of 0.23-3.6 μg/ml, and was more effective intracellularly than extracellularly. It was further tested for its ability to cooperate with isoniazid, streptomycin, pyrazinamide, rifampin, rifabutin, penicillin and ethambutol (EMB) against intramacrophage M. tuberculosis and M. avium. CPZ enhanced the effectiveness of most of the drugs tested against intracellular mycobacteria. However, the combination of CPZ and EMB did not result in augmented antimycobacterial activity.

Mycobacterium tuberculosis and Mycobacterium avium multiply in cultured human macrophages (MP) within membrane-enclosed vesicles. These vesicles are generally assumed to be acidic. The evidence most frequently cited for this assumption is that pyrazinamide, which requires an acid pH to be effective, is effective and streptomycin, which loses most of its activity at a low pH, is poorly effective against tubercle bacilli. This assumption was tested by using the two weak bases chloroquine and NH4C1 to raise the pH of acidic vesicles in MP experimentally infected with M. tuberculosis or M. avium. An immunocytochemical locator of acidic regions in the MP was used to monitor the association of intracellular bacilli with acidity. MP were infected with M. tuberculosis or M. avium and incubated with various combinations of the drugs and the weak bases. Replication of the bacteria in the MP was measured by culture counts. Intracellular associations of the mycobacteria with acidity were assessed by electron micrographs and by using the weak base 3-(2,4dinitroanilino)-3'-amino-N-methyl dipropylamine, which was detected with colloidal gold-labeled antibodies. It was confirmed by immunocytochemistry that both chloroquine and NH4Cl raise the pH of acidic vesicles in the infected MP. However, neither caused any pH-related change in the antimycobacterial activities of pyrazinamide or streptomycin or of the pH-independent drug isoniazid. Immunochemical analyses showed acidity to be associated with killed but not living mycobacteria in the MP. These findings suggest that living M. tuberculosis and M. avium are located in human MP in vesicles which are not acidic.

Historically, sunlight has seemed to fortify antituberculosis resistance. Evidence is presented here suggesting a role for vitamin D in this effect. The active metabolite of this photosynthesized vitamin, 1,25-dihydroxyvitamin D3 (1,25D), promotes maturation and activation of human monocytes and macrophages (MPs). Therefore, it was tested for ability to protect MPs against virulent tubercle bacilli. MPs were derived by 7-day culture from blood monocytes, infected with the bacilli, and exposed to 1,25D in several regimens. Their inhibition of bacilli was measured by lysing samples of the cultures at 0, 4, and 7 days after infection and making bacillary CFU counts from serial dilutions of the lysates. 1,25D enabled MPs to slow or stop bacillary replication. Autologous serum supported the 1,25D-induced protection because the vitamin was not effective in medium supplemented with a serum substitute and was less effective in a heterologous AB serum than in autologous serum. The protection developed rapidly and could be induced even when 1,25D was added 3 days after infection. A concentration on the order of 4 ,tg/ml was needed for protection by the regimens used in these experiments. That is considerably higher than normal circulating concentrations of 1,25D but could be reached in infectious granulomas, because MPs can make 1,25D from precursor 25-hydroxyvitamin D3. The precursor circulates at levels 103 higher than those of 1,25D and is directly influenced by dietary intake or photosynthetic production of vitamin D. These results identify 1,25D as an immunomodulator which can reproducibly activate human MPs to express tuberculoimmunity. They connect vitamin D, sunlight, and tuberculoimmunity and suggest that vitamin D should be considered a vital factor in the practical control of tuberculosis.